Ancient Lava Flows and Plutons

Pamela J. W. Gore
Georgia Perimeter College

Lava Flows

Columnar jointing, Orange Mountain Basalt, I-280, West Orange, NJ

Columnar jointing in basalt, Culpeper Basin, Virginia

Plutons

Subsurface igneous bodies

Concordant Plutons

The pluton parallels the structure in the surrounding rock.

sill
laccolith

Discordant Plutons

The pluton cuts across the structure in the surrounding rock.

dike - width ranges from less than 1 cm to 1 km
stock - ranges in size (area) from 1 km²to 100 km²
batholith - the largest intrusive body. A batholith covers 100's of square kilometers of area.

Sills

The Palisades along the western shore of the Hudson River, Palisades Park, NJ. The Palisades Sill is one of the largest and best-known sills in the U. S., and is about 300 m thick.

Dikes

Pegmatite dike or vein in granite.

Weathered Triassic-Jurassic diabase dike (yellow) surrounded by gray contact metamorphic aureole. Diabase dike intrudes into red siltstone. Deep River Basin, Borden Brick and Tile Quarry, Bilboa (Durham), NC.